1. Field of the Invention
The present invention relates to a side-channel pump with an impeller arranged rotatably in a pump housing having an inlet channel and an outlet channel, the impeller including rotor blades arranged for pumping a liquid from the inlet channel to the outlet channel, and guide means for guiding the impeller in an axial position and/or a radial position.
2. Description of the Related Art
Side-channel pumps with impellers having rotor blades, inlet and outlet channels, and guide means for guiding the impeller in a radial and/or axial position are often used in motor vehicles for delivering fuel or washer fluid and they are known in practice. The pump housing of the known side-channel pump is composed of two parts which are held at a distance from one another by an intermediate ring having dimensions corresponding to the height of the impeller. As guide means, the known side-channel pump has pockets arranged in the area between the center of the impeller and the area of the rotor blades. The pockets are designed so that a small proportion of the medium to be pumped collects therein. The impeller floats on the medium held in the pockets. Radial forces acting on the impeller are generally absorbed by the bearing arrangement of a drive shaft of an electric motor that drives the side-channel pump.
A problem with the known pump is that the guidance of the impeller is extremely inadequate and generally does not prevent the impeller from rubbing against the housing. The rubbing of the impeller against the housing creates frictional losses which reduce the efficiency of the side-channel pump. The inadequate guidance also causes the gap between the impeller and the pump housing to fluctuate in the area of the rotor blades. The fluctuation in this gap leads to a further reduction in the efficiency of the side-channel pump.
It is an object of the present invention to provide a side-channel pump such that frictional losses are avoided in as reliable a manner as possible.
The object according to the present invention is met by arranging guide means in the area of a radially outer rim of an impeller of the side-channel pump.
According to the present invention, the guide means extend over only a particularly small area of the impeller. In the area of the radially outer rim, the liquid to be pumped has a particularly high pressure due to friction on the impeller and centrifugal forces. As a result, the guide means arranged at the radially outer rim allow the transmission of large guiding forces to the impeller. The radially outer area may furthermore be manufactured with a particularly high accuracy with a low outlay in manufacture. The present invention obviates the requirement for further component for guiding the impeller. As a result, the cost of the side-channel pump according to the invention is furthermore particularly low.
The guide means may, for example, include a ring with a plurality of individual skids. A further contribution to reducing the cost of manufacturing the side-channel pump according to the invention is made if the guide means have at least one guide surface which lies opposite a corresponding area of the housing with an intended guide clearance.
According to another embodiment of the present invention, a first gap between the area of the impeller that has the rotor blades and the housing is configured independently of a second gap arranged in the area of the guide means. In this embodiment, the guide means have a change in cross section arranged in the area of the rim of the impeller. The areas of the impeller that form the change in cross section are each designed as guide surfaces that lie opposite the housing with an intended guide clearance. As a result, the second gap of the guide clearance that determines the friction and guiding forces on the impeller is set to an intended value independently of the first gap in the area of the rotor blades, the first gap determining the characteristic of the feed pump.
According to a further embodiment of the present invention, the change in cross section may be produced at a particularly low cost if the change in cross section is abrupt, i.e., a step change.
The impeller may be guided both axially and radially by a single guide surface if the change in cross section is designed as a chamfer, i.e., a beveled edge.
In side-channel pumps according to the present invention provided for delivering fuel or washer fluid, the change in cross section designed as a chamfer provides the impeller with adequate radial and axial guidance if the guide surface is arranged at an angle of about 30 to 60xc2x0 to the end of the impeller.
It is often sufficient to support the impeller axially against gravitational force in only one direction and to arrange the electric motor for driving the impeller above the impeller if the side-channel pump according to the present invention is provided for delivering full or washer fluid. In this case, the guide means require a single guide surface on only one side. In a further embodiment of the present invention, the gap between the impeller and the housing in the area of the rotor blades may be set with particular accuracy if the rim has respective guide surfaces, each facing one end. This arrangement contributes to a further improvement in the efficiency of the side-channel pump according to the present invention.
According to yet another embodiment of the present invention, the requirement for costly intermediate rings to be inserted into the pump housing may be avoided by arranging two mutually opposite housing parts surrounding the impeller so that they border one another in the area of the maximum diameter of the impeller. It is thereby furthermore possible to set the gap with particularly narrow tolerances. This contributes to a further increase in the efficiency of the side-channel pump according to the present invention.
Other objects and features of the present invention will become apparent from the following detailed description considered in conjunction with the accompanying drawings. It is to be understood, however, that the drawings are designed solely for purposes of illustration and not as a definition of the limits of the invention, for which reference should be made to the appended claims. It should be further understood that the drawings are not necessarily drawn to scale and that, unless otherwise indicated, they are merely intended to conceptually illustrate the structures and procedures described herein.